Finite element analysis of ultrasonically assisted turning of Inconel 718

The paper deals with finite element (FE) modelling of ultrasonically assisted turning (UAT). In this processing technology, high frequency vibration (frequency, f≈20 kHz; amplitude, a≈10 μm) is superimposed on the movement of the cutting tool. Ultrasonic vibration yields for a nickel-base alloy Inconel 718 a decrease in cutting forces and working temperatures as well as a superior surface finish. The developed FE model allows transient, coupled thermomechanical modelling of both ultrasonic and conventional turning (CT) of elasto-plastic materials. The Johnson–Cook material model is adopted for Inconel 718 in simulations. Comparative analyses of temperature distribution in the cutting region and cutting tool are carried out for both turning schemes. Plastic strains during cutting and residual strains in the machined layer are analysed and compared with the results of nanoindentation tests of Inconel 718 specimens processed with and without application of ultrasonic vibration. Overall reduction in cutting forces and temperatures for ultrasonic turning in comparison to conventional turning is explained.